Cytokine Induced Killer Cells as Promising Immunotherapy for Solid Tumors
Cytokine-Induced Killer (CIK)

Author: Michela Cangemi
Date: 08/09/2014


Malignante has become a major cause of human deaths world wide nowadays. Unfortunately, traditional therapies including surgery, chemotherapy and radiotherapy often fail to eradicate tumor lesions completely and tend to result in many adverse events. Thus, novel approaches for curing malignancies are urgently necessary. In recent years, immunotherapy has emerged as an efficacious treatment modality with encouraging efficacy and slight adverse events in cancer therapy. Among various kinds of immunotherapy, cytokine-induced killer (CIK) cells therapy has moved from the “bench to bedside” and been suggested as a promising method.

Cytokine-induced killer (CIK) cells are a subset of T lymphocytes with a NK T cell (NKT) phenotype expressing both the CD3 and the CD56 markers. CIK cells are mostly CD8+, express a heterogeneous TCR repertoire, are CD1d independent and can be reproducibly expanded in vitro from bone marrow or PBMC over a 3-week time period. CIK cells are capable of a broad MHC-unrestricted anti-tumor activity against both syngeneic and allogeneic hematological malignancies, as documented both in vitro and in vivo by murine models (Alloreactivity and anti-tumor activity segregate within two distinct subsets of cytokine-induced killer (CIK) cells: implications for their infusion across major HLA barriers, 2008).

CIK cells represent a promising tool in the sce-nario of cancer adoptive immunotherapy strategies. Their easy and inexpensive ex-vivo expansion, along with the MHC-unrestricted tumor killing ability may overcome some crucial problems that have limited the diffusion and clinical translation of other immuno-therapy approaches.

Killing activity of CIK cells against Gastrointestinal Tumors

Tumors of the gastrointestinal (GI) system constitute a major part of the cancer incidence and mortality statistics. Worldwide, colorectal cancer is the most frequent type of GI cancer: it is the third most common cancer in men and the second most common in women. Moreover, colorectal cancer accounts for the largest share of GI cancer-related deaths in women, while liver cancer is the most common cause of death among GI tumors of men.
Adoptive cell immunotherapy might be used in combination with standard therapies—as adjuvant postsurgical treatment and as palliative treatment—to improve survival and quality of life of GI cancer patients. Cytokine-induced killer (CIK) cells have the best credentials to be effective in this therapeutic approach. Compared to lymphokine-activated killer (LAK) cells, CIK cells can be obtained more easily and reveal a higher tumor-specific cytotoxic activity. (Clinical Studies Applying Cytokine-Induced Killer Cells for the Treatment of Gastrointestinal Tumors, 2013).

Gastric Cancer

Jiang et al.(Treatment of advanced gastric cancer by chemotherapy combined with autologous cytokine induced killer cells,2006) provide a study applying CIK cells in combination with chemotherapy in patients with advanced gastric cancer who had all undergone palliative gastrectomy. After gastrectomy, twenty-five patients were treated with three cycles of folinic acid, 5-fluorouracil (5-FU), and oxaliplatin (FOLFOX) chemotherapy. Thirty-two patients were treated with FOLFOX chemotherapy plus autologous CIK cell therapy consisting of five transfusions of CIK cells (1 × 109) after each chemotherapy. In both treatment groups, serum levels of tumor markers were significantly (𝑃 < 0.05) lower after therapy. The decrease was more pronounced in the patient group receiving additional CIK cell therapy. In the beginning, there was an increase in the cumulative survival rate of the patients treated with CIK cell transfer but after two years, there was no difference in survival between the two groups. Still, the authors conclude that there is a benefit of combined chemo- and CIK cell therapy for patients with advanced gastric cancer.

Wang et al.(A pilot study of chemotherapy combined with intraperitoneal perfusion of cytokine-induced killer cells for advanced gastric cancer patients with ascite,2013) published a study combining capecitabine and oxaliplatin chemotherapy with intraperitoneal (i.p.) perfusion of CIK cells. Forty-two advanced gastric cancer patients with ascites were enrolled in two groups: the chemotherapy group (22 patients) and the combination group (chemotherapy plus CIK perfusion; 20 patients). The combination of chemotherapy and CIK cells was well tolerated, and there were no serious adverse reactions after CIK perfusions. Compared to chemotherapy alone, the combined therapy was able to reduce the volume of 2-cycle peritoneal fluid drainage (𝑃 = 0.018). Patients additionally treated with CIK cells showed a longer median time to progression (TTP; 𝑃 = 0.001) and a superior OS (𝑃 = 0.006)

Hepatocellular Carcinoma

Despite the evolving new medical treatments such as the tyrosine kinase inhibitor sorafenib, therapy of HCC is still challenging. A small clinical trial about CIK cell therapy in HCC patients was published by Shi et al (Autologous cytokine induced killer cell therapy in clinical trial phase I is safe in patients with primary hepatocellular carcinoma, 2004) enrolled thirteen patients with diagnosed HCC. All patients had liver cirrhosis and more than twenty years of chronicHBV infection. Autologous CIK cells were reinfused i.v. at days ten, thirteen, and fifteen of CIK cell culture. Before treatment and ten days after CIK cell therapy, the patients’ PBMCs were analyzed using a flow cytometer: percentages of CD3+CD8+, CD25+, and particularly of CD3+CD56+ cells were significantly increased (𝑃 < 0.05). Patients were followedup for up to 108 days after CIK cell therapy. At that time, the composition of lymphocyte subpopulations was still similar to the levels determined ten days after therapy. This indicates that the induced changes in the subpopulations can last for at least 108 days.

Zhao et al. (Cytokine-induced killer cell fusion to lower recurrence of hepatocellular carcinoma after transcatheter arterial chemoembolization sequentially combined with radiofrequency ablation: a randomized tria,2006) included 64 HCC patients in a CIK cell therapy study. All patients had undergone transarterial chemoembolization (TACE) and additional radiofrequency ablation (RFA).No residual tumor or extrahepatic metastases could be detected. Each of the 33 patients in the study group received eight autologous CIK infusions every three to four weeks either via the peripheral vein or the hepatic artery.
The 31 patients in the control group were given no additional treatment. After a relatively short followup of one year, 29 patients in the study group and 23 patients in the control group were recurrence-free.

Colorectal Cancer

The only clinical trial with CIK cells including colorectal cancer patients was published by
Schmidt-Wolf et al. in 1999 (Phase I clinical study applying autologous immunological effector cells transfected with the interleukin-1 gene in patients with metastatic renal cancer, colorectal cancer and lymphoma). Here, CIK cells were transfected with a plasmid containing the IL-2 gene. Ten patients with metastatic disease were included in this study—seven patients with colorectal cancer, two patients with lymphoma, and one patient with renal carcinoma. The patients received one to five i.v. infusions of IL-2-transfected CIK cells and five infusions of untransfected CIK cells; the second treatment
cycle followed three weeks after the first one. CIK cell therapy was well tolerated; only three patients developed WHO grade 2 fever. Transfected cells could be detected in the patients’ blood for up to two weeks after immunotherapy.

Killing activity of CIK cells against Bone and Soft-Tissue Sarcoma

Bone and soft-tissue sarcomas (STS) are a heterogeneous group of mesenchymal tumors. Regardless their heterogeneity, advanced, not surgically amenable, bone sarcoma and STS are linked by a common dismal clinical prognosis. Although new hope has been brought by molecular targeted therapies, results are still insufficient. Indeed, metastatic and unresectable diseases remain incurable with less than 10% of the patients alive after 5 years. As new approaches are urgently needed, adoptive immunotherapy is considered a promising option to be explored. In this scenario, reliable patient-specific preclinical models are
crucial to provide basis for an effective clinical translation of this strategy.
To test the antitumor activity of CIK cells expanded from all our patients, the authors started evaluating their ability to kill in vitro allogeneic bone sarcoma and STS cell lines (MNNG-HOS; SJSA 1; MES-SA). The cytotoxicity test was conducted at the end of the ex vivo expansion and showed an efficient killing even if
variable among patients. The mean specific tumor killing was 81% 76%, 61%, and 44% at 40:1, 20:1, 10:1, and 5:1 effector/target ratio. Next, the authors assessed the ability of patient-derived CIK cells to kill autologous targets from all the 8 primary tumor cell cultures. Results showed mean specific killing of 83%, 79%, 74%, and 62% at a 40:1, 20:1, 10:1, and 5:1 effector/target ratio. The intensity of killing against autologous targets was comparable among different histotype and was not inferior to that observed with allogeneic CIK cells assessed in parallel versus the same primary tumor cells.
To more closely simulate the real clinical situation, you tested the activity of patient-derived CIK cells in vivo against autologous tumor xenografts in NOD/SCID mice. Mice were implanted with primary cells of metastatic pleomorphic sarcoma and received 9 weekly intravenous infusions of mature autologous CIK cells (107 per week). A significant reduction of tumor growth was observed in treated mice compared with untreated controls, mean volumes at the end of experiment were in treated mice 807 mm3 (SEM, 138) versus 1,702 mm3 (SEM, 441) of controls. Evaluation of residual proliferative index, by Ki- 67 analysis, on residual tumor samples explanted at the end of the experiment revealed a significant reduction in treated mice compared with controls (mean, 4.5; SEM, 1.2 vs. 9.3; SEM, 0.5; P ¼ 0.009). These last data are consistent with recent observation from immunotherapy clinical trials, requiring additional metabolic or histologic data beyond the conventional Response Evaluation Criteria in Solid Tumors (RECIST) to evaluate clinical responses. At the end of the experiment, you confirmed the presence of CIK cells infiltrating the autologous tumor. (Cytokine-Induced Killer Cells Eradicate Bone and Soft-Tissue Sarcoma, 2013)


The clinical studies discussed here prove CIK cell therapy to be an effective treatment option—after or along
with conventional therapies—for patients with gastrointestinal tumors. In addition, as it was shown to be safe and not to induce major adverse effects, CIK cell therapy is a valuable alternative for patients not able or willing to tolerate side effects of conventional chemotherapy. In summary, CIK cell therapy provides a promising approach in cancer therapy. CIK cells have a favorable biology with non-MHC-restricted tumor targeting and uncomplicated isolation and cultivation. In all studies, CIK cell therapy was well tolerated and superior to conventional therapies alone. There are several questions yet to be elucidated, for example, the optimal application schedule and the best therapeutic combination with conventional treatment modalities.

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